JP2006235138A - Plastic primary coated optical fiber and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a plastic primary coated optical fiber (POF) having low transmission loss by improving adhesion at the fitting surface of a preform. <P>SOLUTION: A cylindrically shaped first member 14 which is made of a core material 30 made of a core material 31 and an inner clad material 32 and an inner side pipe member 12 arranged on the outer circumference of the core material 30 and a second member 18 made of a cylindrical and hollow outside pipe material 17 are respectively produced and performed reduced-pressure drying using a vacuum dryer. At that time, the drying temperature is set equal to or higher than 50°C and equal to or lower than 100°C and the drying time is set equal to or more than 10 hours and equal to or less than 100 hours as the drying conditions. Then, the first member 14 is inserted into the hollow section of the second member 18 to make a preform 21. By heat extending and line drawing the preform 21, the first member 14 and the second member 18 are simultaneously extended and mutually welded to form the POF. Thus, the adhesion at the fitting surface formed by each member is made superior, generation of white muddiness is suppressed and the POF having low transmission loss is obtained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a plastic optical fiber and a method for manufacturing the same.

  BACKGROUND ART An optical fiber that is an optical transmission body composed of a core that transmits light and a clad that covers the outer periphery of the core is used in various fields because it can transmit information at a high speed and with a large capacity. In such an optical fiber, a plastic optical fiber (Plastic Optical Fiber) that has excellent properties such as molding processability, flexibility, and impact resistance, is safe and inexpensive, and has low transmission loss. ; POF) is drawing attention.

  Among them, the graded index (GI type) POF in which the core is formed so that the refractive index continuously increases toward the center thereof is gradually changed by continuously changing the refractive index. Can be refracted into light and confined in the core, or by using the fact that the speed of light in the medium is inversely proportional to the refractive index, the light speed increases with increasing distance from the center. Attention has been paid to the fact that the light that travels straight from the one end to the other end of the optical fiber can be made the same in order to make the transmission waveform difficult to break.

  In general, a POF manufacturing method including a GI-type POF is produced by producing a plastic optical fiber preform (hereinafter referred to as a preform) composed of a core material and a clad material that constitute a core and a clad, respectively. A POF having a predetermined diameter is manufactured by drawing by heating and drawing. Moreover, when the outer periphery of this POF is covered with a covering material to form a protective layer, a plastic optical fiber cord (or a plastic optical fiber core wire) can be produced. Thus, when a protective layer is formed on the outer periphery of POF, its heat resistance and weather resistance can be improved. In the present invention, the operation of coating the surface of a member with a coating material will be described below as a coating process.

  However, when the coating process is performed, bending loss occurs in the POF due to the heat generated during coating, the molten resin as the coating material, or the non-uniformity of the flow of the molten resin, and the like. As a result, there arises a problem that the transmission loss of POF increases. Conventionally, when manufacturing POF, a plurality of polymer components having different refractive indexes are used and polymerized in order to produce a cylindrical tube, and the cylindrical tubes having different refractive indexes are multiplexed on the same axis. POF was produced by heating and stretching the multi-layered pipe as a preform. However, in such a production method, white turbidity may occur at the interface formed by polymer components having different refractive indexes depending on the difference in composition. When POF is produced using such a preform, As a result, the transmission loss increases.

  As a method for solving these problems, a member (second member) having a refractive index distribution and transmitting light is inserted into a cylindrical tube (first member) that plays a role of a protective layer in advance. A method for producing a POF by drawing a preform and stretching the preform at the same time to draw a POF (see, for example, Patent Document 1), or a plurality of cylindrical tubes made of polymers having different refractive indexes. A method has been proposed in which a plurality of cylindrical tubes are arranged on the same axis, and POF is manufactured by drawing them while being fused with each other by heating them (see, for example, Patent Document 2). . In the present invention, as described in Patent Documents 1 and 2, after the first member and the second member are produced in separate steps, a preform is formed by fitting them, and this is drawn to produce a POF. This method is called a fitting POF manufacturing method. A contact interface generated when two different members are fitted together is referred to as a fitting surface.

In the method described in Patent Document 1, since a POF in which a cylindrical tube already serving as a protective layer is arranged on the outer periphery can be manufactured, heat resistance and weather resistance are excellent even without coating a coating material. POF can be obtained. Therefore, since a coating process is unnecessary, a problem that occurs during coating does not occur. In the method described in Patent Document 2, since the drawing is performed while the cylindrical tubes are thermally fused together, the reaction at the interface formed by the cylindrical tubes is sufficiently prevented regardless of the material constituting the polymer. Since the formation of one polymer domain is suppressed, the occurrence of white turbidity at the interface can be suppressed.
JP-A-9-178961 JP-A-11-344623

  However, in the manufacturing method described in Patent Document 1, the fitting surface formed by inserting the second member into the hollow portion of the first member that is formed in advance as the protective layer contacts the two without fitting well. In some cases, when a POF is produced using a preform with such mismatching, there is a problem that the transmission loss of the POF increases. Also, in the POF manufacturing method described in Patent Document 2, as in Patent Document 1, mismatch occurs at an interface formed by a plurality of cylindrical tubes, and as a result, transmission loss of POF increases. There was a risk that this would occur.

  The present invention produces a preform having excellent adhesion on the fitting surface formed when the first member and the second member are fitted together, and is drawn by heating and stretching to reduce transmission loss and It is an object of the present invention to provide a POF with reduced bending loss and a method for manufacturing the same.

  In the POF manufacturing method according to the present invention, a columnar first member including a core material including a core and a clad, and an inner pipe disposed on an outer periphery of the core material, and an outer periphery of the first member are disposed. A second member formed of a cylindrical outer pipe, and after drying at least one of the first member and the second member under reduced pressure under a predetermined drying condition, The first member is inserted into a hollow portion to form a preform, which is heated and stretched to draw POF, thereby producing POF. Moreover, the temperature at the time of the said drying is 50 degreeC or more and 100 degrees C or less, It is preferable that the drying time is 10 hours or more and 100 hours or less.

  It is preferable that the material constituting the core is an acrylic resin, and the core has a refractive index distribution in which the refractive index gradually increases as it goes to the center in the radial direction. It is preferable that the material constituting the second member is one or two or more of a mixed material obtained by mixing an acrylic resin, a vinylidene fluoride resin, and a polymethyl methacrylate / vinylidene fluoride resin. In addition, it is preferable that the thickness of the said 2nd member is 1 mm or more and 100 mm or less.

  The POF of the present invention is manufactured by any one of the above-described POF manufacturing methods.

  According to the present invention, a columnar first member composed of a core material composed of a core and a clad, an inner pipe disposed on the outer periphery of the core material, and a cylindrical shape disposed on the outer periphery of the first member. A second member made of an outer pipe is respectively produced, and at least one of the first member and the second member is dried at a temperature of 50 ° C. or higher and 100 ° C. or lower, and the drying time is 10 hours or longer and 100 After drying under reduced pressure for less than the time, the first member was inserted into the hollow part of the second member to form a preform, and this was heated and stretched to draw POF, so that POF was manufactured. Moisture or excess plasticizer contained in each of the first member and the second member and bubbles on the fitting surface can be sufficiently removed, and the adhesion of the fitting surface formed by each member. Improve It is possible. As a result, it is possible to produce a preform with reduced mismatching and white turbidity on the mating surface, and even if this is heated and stretched, moisture, plasticizer, etc. are not foamed. Transmission loss POF can be manufactured.

  The material constituting the core is an acrylic resin, and the core has a refractive index distribution in which the refractive index gradually increases toward the center in the radial direction. POF can be manufactured.

  Further, the material constituting the second member may be one type or two or more types among mixed materials obtained by mixing acrylic resin, vinylidene fluoride resin, polymethyl methacrylate / vinylidene fluoride resin, Since the thickness of the member is 1 mm or more and 100 mm or less, the occurrence of white turbidity due to the difference in the composition of the polymers on the fitting surface can be suppressed, so that a high-strength POF can be produced.

  Embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments. FIG. 1 is a process diagram for explaining a POF manufacturing process.

  As shown in FIG. 1, the POF manufacturing process of the present invention includes a process for manufacturing the first member 14 and the second member 18, and a fitting process 20 for manufacturing the preform 21 by fitting these members together. And a stretching step 23 for obtaining POF 23 by drawing the preform 21 by heating and stretching.

  First, the 1st member 14 and the 2nd member 18 are produced, respectively. In FIG. 2, the fitting process figure at the time of producing the preform 21 is shown. As shown in FIG. 2, the 1st member 14 consists of the core material 30 and the inner side pipe material 12 distribute | arranged so that the outer periphery may be covered. The core material 30 includes a core material 31 and an inner clad material 32 disposed so as to cover the outer periphery of the core material 31. The second member 18 includes an outer pipe member 17 that is arranged so as to cover the outer periphery of the first member 14. In the present invention, a member covering the outer periphery of the core member 30 is referred to as a pipe member, a member in contact with the core member 30 is referred to as an inner pipe member 12, and a member disposed on the outer periphery thereof is referred to as an outer pipe member 17.

  In the production of the first member 14, first, the cylindrical inner pipe member 12 is produced in the inner pipe production process 11. As shown in FIG. 2, the inner pipe member 12 forms an outer shell portion of the first member 14 constituting the preform 21. The material constituting the inner pipe member 12 and the formation method thereof will be described later.

  After the inner pipe member 12 is manufactured, the core member 30 is formed in the hollow portion of the inner pipe member 12 in the core member manufacturing step 13 (see FIG. 2). First, a polymerizable compound (hereinafter referred to as an inner clad material monomer) for generating the inner clad material 32 is injected into the hollow portion of the inner pipe material 12 and polymerized to form the inner clad material 32. . At this time, the inner clad material monomer is polymerized so that the center of the circular cross section becomes a cavity, thereby generating the inner clad material 32. In addition, when an interfacial gel polymerization reaction, which is a kind of bulk polymerization in which a predetermined reaction proceeds, occurs when the polymer expands or dissolves when the polymerizable compound comes into contact with the polymer and soaks into the polymer, The previously formed polymer may be dissolved. In this case, due to the generation reaction of the core material 31 to be described later, the previously formed inner clad material 32 is integrated with the core material 31, and the inner clad material 32 is not recognized.

  Next, a polymerizable compound (hereinafter referred to as a core material monomer) for generating the core material 31 is injected into the inner clad material 32, and this is polymerized to generate the core material 31. In this way, the first member 14 having a cylindrical shape and a multi-layer structure in which the core material 30 including the core material 31 and the inner clad material 32 is formed inside the inner pipe material 12 is manufactured. Subsequently, the produced first member 14 is dried while reducing the pressure in the first reduced-pressure drying step 15. Details of the first reduced-pressure drying step 15 will be described later.

  In the production of the second member 18, in the outer pipe material production step 16, a cylindrical outer pipe material 17 is produced (see FIG. 2). The material constituting the outer pipe member 17 and the manufacturing method thereof will be described later. Further, the produced outer pipe member 17 is dried while being decompressed in the second decompression drying step 19. The second vacuum drying step 19 will also be described later.

  After producing the 1st member 14 and the 2nd member 18, in the fitting process 20, these are fitted together and the preform 21 is produced (refer FIG. 2). In the fitting step 20, the first member 14 is inserted into the hollow portion of the cylindrical second member 19. The preform 21 thus produced is subjected to a stretching step 22, and the POF 23 is manufactured by drawing by heating and drawing by a predetermined method.

  As shown in FIG. 2, the first member 14 includes an inner pipe member 12 and a core member 30, and the core member 30 includes a core member 31 and an inner clad member 32. In the present invention, the first member 14 is a member that transmits light through the optical fiber. The second member 19 is made of a cylindrical hollow outer pipe material 18. In addition, both the first member 14 and the second member 19 have the same outer diameter and inner diameter in the longitudinal direction and uniform thickness. Therefore, in the first member 14, the inner diameter of the inner pipe material 12 is equal to the outer diameter of the inner cladding material 32, and the outer diameter of the core material 31 is equal to the inner diameter of the inner cladding material 32. In the present invention, the inner pipe member 12 and the outer pipe member 18 are collectively referred to as a pipe member 33 and will be described below.

  In the present invention, the preform 21 is produced by inserting the first member 14 into the hollow portion of the second member 18 (see FIG. 2). At this time, the outer peripheral surface of the first member 14 serving as a fitting surface of these members and the inner peripheral surface of the second member 19 are excellent in adhesion, and it is preferable to suppress the occurrence of mismatch as much as possible. . Therefore, it is preferable that the outer diameter of the first member 14 and the inner diameter of the second member 19 be as equal as possible.

  In the present invention, the surface roughness Ra on the outer peripheral surface of the first member 14 and the inner peripheral surface of the second member 18 is preferably 0.5 μm or less, and this value can be made as small as possible. More preferred. The surface roughness Ra is extracted from the roughness curve by the reference length 1 in the direction of the average line, the average length corresponding to the distance between adjacent local peaks is obtained, and the average value between the many local peaks is measured in micrometers. (Μm). This value is the surface roughness Ra on the outer peripheral surface of the first member 14 and the inner peripheral surface of the second member 18. When the surface roughness Ra is larger than 0.5 μm, mismatching occurs on the fitting surface of the preform 21, so that the low transmission loss POF 23 cannot be manufactured. On the other hand, when the preform 21 is produced by fitting the first member 14 and the second member 18 whose surface roughness Ra is adjusted so as to satisfy the above range, the adhesion on the fitting surface is improved. Therefore, the occurrence of cloudiness can be suppressed. In addition, it is possible to suppress deterioration of transmission loss due to mismatch caused by contact between the two on the fitting surface. Therefore, when the preform 21 having high adhesion on the fitting surface is used as described above, the POF 23 with low transmission loss can be manufactured.

  On the outer peripheral surface of the first member 14 and the inner peripheral surface of the second member 18, it is preferable to perform a polishing process that appropriately adjusts the surface roughness Ra so as to express the surface roughness Ra as described above. . For example, in order to make the surface roughness Ra of the first member 14 within the above range, after the first member 14 composed of the core material 30 and the inner pipe material 12 is produced, the surface disposed adjacently is smooth. The surface of the 1st member 14 should just be smoothed by installing in the dent formed with a simple pipe and rotating this pipe. On the inner peripheral surface of the second member 18, a method of polishing with an abrasive or a polishing sheet may be mentioned so as to obtain a desired surface roughness Ra. This method can also be applied to the first member 14. However, in the present invention, the method for adjusting the surface roughness Ra is not particularly limited as long as it is a method capable of expressing the desired surface roughness Ra.

  The outer pipe material 17 that is the second member 18 preferably has a thickness of 1 mm or more and 500 mm or less, more preferably 1 mm or more and 200 mm or less, and particularly preferably 1 mm or more and 100 mm or less. When the thickness is 500 mm or more, POF 23 having excellent heat resistance and weather resistance can be obtained. However, since the thickness of the outer pipe material 17 that can be a protective layer is too thick, the molding processability is lowered. . On the other hand, if it is 1 mm or less, it is too thin to allow the POF 23 to exhibit sufficient heat resistance and weather resistance.

  As shown in FIG. 3, the POF 23 includes a core 40 and a pipe 41. The core 40 and the pipe 41 are formed by drawing the core material 30 and the pipe material 33 constituting the preform 21 by heating and drawing, respectively. The POF 23 has a structure in which an outermost shell of a member constituted by the core 40 and the inner pipe 44 is covered with an outer pipe 45. At this time, since the outer pipe 45 serves as a protective layer, the POF 23 is excellent in heat resistance and weather resistance. In FIG. 3, the boundaries between the members constituting the core 40 and the pipe 41 are shown for convenience of explanation. However, the clarity of the boundaries differs depending on manufacturing conditions and the like, and may not necessarily be confirmed.

  The POF 23 has a refractive index distribution in which the refractive index gradually increases as the core 40 moves toward the center in the radial direction. As described above, when the refractive index is continuously changed, light can be gradually refracted and confined in the core 40, and the speed of light in the medium is inversely proportional to the refractive index. By increasing the speed with increasing distance from the center, it is possible to make the time for light traveling diagonally and light traveling straight from reaching one end of the optical fiber strand the same, so that the transmission waveform is disrupted. Can be difficult.

  The material used for the first member 14 and the second member 18 is preferably an amorphous polymer so as not to cause light scattering. The material is excellent in adhesion to each other and has mechanical properties such as durability. It is preferable that the polymer is excellent in properties and excellent in heat and humidity resistance.

  The material constituting the core material 30 (inner clad material monomer and core material monomer) is preferably an acrylic resin. Examples include (meth) acrylic esters ((a) fluorine-free (meth) acrylic acid ester, (b) fluorine-containing (meth) acrylic acid ester), and the like. Further, as other materials, (c) styrene compounds, (d) vinyl esters, bisphenol A which is a raw material of polycarbonates, and the like may be used as the polymerizable compound. The core material 30 can be formed from these homopolymers, copolymers composed of two or more of these monomers, or a mixture of homopolymers and / or copolymers. Among these, a composition containing (meth) acrylic acid esters as a polymerizable monomer can be preferably used.

  As the above (a) fluorine-free methacrylic acid ester and fluorine-free acrylic acid ester, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, tert-butyl methacrylate, benzyl methacrylate, phenyl methacrylate, methacrylic acid Examples thereof include cyclohexyl, diphenylmethyl methacrylate, tricyclo [5.2,1.02,6] decanyl methacrylate, adamantyl methacrylate, isobornyl methacrylate, norbornyl methacrylate, and the like. Methyl acrylate, ethyl acrylate, acrylic acid- Examples include tert-butyl and phenyl acrylate.

  (B) As fluorine-containing acrylic ester and fluorine-containing methacrylate ester, 2,2,2-trifluoroethyl methacrylate, 2,2,3,3-tetrafluoropropyl methacrylate, 2,2,3,3,3 -Pentafluoropropyl methacrylate, 1-trifluoromethyl-2,2,2-trifluoroethyl methacrylate, 2,2,3,3,4,4,5,5-octafluoropentyl methacrylate, 2,2,3, Examples include 3,4,4-hexafluorobutyl methacrylate.

  (C) Styrene compounds include styrene, α-methylstyrene, chlorostyrene, bromostyrene, and (d) vinyl esters include vinyl acetate, vinyl benzoate, vinyl phenyl acetate, vinyl chloroacetate, and the like. Can be mentioned. Of course, the present invention is not limited to these, and the refractive index of a polymer composed of a polymerizable compound alone or a copolymer may have a predetermined refractive index distribution in the molded body when molded into an optical transmission body. In addition, it is preferable to determine the type and composition ratio.

  Moreover, the material which comprises the 2nd member 18, ie, the material which comprises an outer pipe material, among the mixed materials which mixed the above acrylic resin, vinylidene fluoride resin, polymethylmethacrylate / vinylidene fluoride resin, It is preferable to use one type or two or more types. In addition to the materials described above, examples of these materials include copolymers of methyl methacrylate (MMA) and fluorinated (meth) acrylates such as trifluoroethyl methacrylate (FMA) and hexafluoroisopropyl methacrylate. In addition, a copolymer of MMA and an alicyclic (meth) acrylate such as (meth) acrylate having a branch such as tert-butyl methacrylate, isobornyl methacrylate, norbornyl methacrylate, tricyclodecanyl methacrylate, etc. is there. When these polymers contain hydrogen atoms (H), the hydrogen atoms are preferably substituted with deuterium atoms (D), thereby reducing transmission loss, particularly in the near infrared region. It is possible to reduce the transmission loss at the wavelength. Moreover, in the material which comprises an inner side pipe material, any said material can be used.

  Furthermore, in order to use POF23 for near-infrared light, absorption loss due to the C—H bond constituting the polymer occurs, which is described in Japanese Patent No. 3332922 and Japanese Patent Application Laid-Open No. 2003-192708. By using a polymer in which C—H bond hydrogen atoms are replaced with deuterium atoms or fluorine, the wavelength range causing this transmission loss can be lengthened, and the loss of transmission signal light can be reduced. can do. Examples of such polymers include deuterated polymethyl methacrylate (PMMA-d8), polytrifluoroethyl methacrylate (P3FMA), polyhexafluoroisopropyl 2-fluoroacrylate (HFIP 2-FA), and the like. it can. In addition, in order not to impair the transparency after polymerization of the compound as a raw material, it is desirable that impurities and foreign substances serving as scattering sources are sufficiently removed before polymerization.

  In the present invention, a polymerization initiator is used when a polymerizable compound is polymerized to obtain a polymer. As the polymerization initiator, for example, there are various types that generate radicals. For example, benzoyl peroxide (BPO), tert-butylperoxy-2-ethylhexanate (PBO), di-tert-butyl peroxide (PBD), tert-butylperoxyisopropyl carbonate (PBI) ) And peroxide compounds such as n-butyl-4,4-bis (tert-butylperoxy) valerate (PHV). 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 1,1′-azobis (cyclohexane-1-carbonitrile), 2,2′-azobis (2-methylpropane), 2,2′-azobis (2-methylbutane), 2,2′-azobis (2-methylpentane), 2,2′-azobis (2,3-dimethylbutane), 2,2 '-Azobis (2-methylhexane), 2,2'-azobis (2,4-dimethylpentane), 2,2'-azobis (2,3,3-trimethylbutane), 2,2'-azobis (2 , 4,4-trimethylpentane), 3,3′-azobis (3-methylpentane), 3,3′-azobis (3-methylhexane), 3,3′-azobis (3,4-dimethylpentane), 3,3'-azobis 3-ethylpentane), dimethyl-2,2′-azobis (2-methylpropionate), diethyl-2,2′-azobis (2-methylpropionate), di-tert-butyl-2,2 ′ -Azo compounds such as azobis (2-methylpropionate). In addition, a polymerization initiator is not limited to these, Moreover, you may use 2 or more types together.

  In order to keep various physical properties such as mechanical properties and thermophysical properties of the polymer uniform throughout, it is preferable to adjust the degree of polymerization. A chain transfer agent can be used to adjust the degree of polymerization. About a chain transfer agent, according to the kind of polymerizable monomer used together, a kind and addition amount can be selected suitably. For the chain transfer constant of the chain transfer agent for each monomer, reference can be made to, for example, Polymer Handbook 3rd Edition (edited by J. BRANDRUP and EH IMMERGUT, published by JOHN WILEY & SON). The chain transfer constant can also be obtained by experiment with reference to Takayuki Otsu and Masaaki Kinoshita "Experimental Method for Polymer Synthesis", Kagaku Dojin, published in 1972.

  Examples of the chain transfer agent include alkyl mercaptans (for example, n-butyl mercaptan, n-pentyl mercaptan, n-octyl mercaptan, n-lauryl mercaptan, tert-dodecyl mercaptan), thiophenols (thiophenol, m-bromothio). Phenol, p-bromothiophenol, m-toluenethiol, p-toluenethiol, etc.) are preferably used. In particular, it is preferable to use an alkyl mercaptan such as n-octyl mercaptan, n-lauryl mercaptan, and tert-dodecyl mercaptan. A chain transfer agent in which a hydrogen atom of a C—H bond is substituted with a deuterium atom or a fluorine atom can also be used. Of course, the chain transfer agent is not limited to these, and two or more of these chain transfer agents may be used in combination.

  About each addition amount of the polymerization initiator mentioned above, a chain transfer agent, and a refractive index regulator, a preferable range can be determined suitably according to the kind etc. of the polymeric compound which is a polymer for cores to be used. In this embodiment, although the polymerization initiator is added so that it may become 0.005-0.050 mass% with respect to the polymeric compound of the core material 30, this addition rate is 0.010-0. More preferably, the content is 0.020% by mass. Moreover, although the said chain transfer agent is added so that it may become 0.10-0.40 mass% with respect to the polymeric compound of the core material 30, this addition rate is 0.15-0.30 mass. % Is more preferable.

  In addition, other additives can be added to the inner pipe member 12, the outer pipe member 17, and the core member 30, or a part thereof within a range that does not deteriorate the optical transmission performance. For example, a stabilizer can be added to the core material 30 or a part thereof for the purpose of improving weather resistance, durability, and the like. Further, for the purpose of improving optical transmission performance, a stimulated emission functional compound for optical signal amplification can be added. By adding the compound, the attenuated signal light can be amplified by the excitation light, and the transmission distance can be improved. For example, it can be used as a fiber amplifier in a part of the optical transmission link. These additives can also be contained in each of the above-mentioned members or a part thereof by adding to the various polymerizable compounds as the raw material and then polymerizing.

  Further, in the inner clad material 31 that forms the inner clad 42 and the core material 31 that forms the core 42, a predetermined amount of a refractive index adjusting agent (hereinafter referred to as a dopant) is added to at least one of the polymers. Mix. As this dopant, a non-polymerizable compound is preferable. When the dopant is added only to the core material 31, the addition ratio is preferably 0.01% by weight to 25% by weight with respect to the polymer as the main component of the core material 31, and is preferably 1% by weight or more. More preferably, it is 20% by weight or less. This makes it easier to control the refractive index distribution coefficient in the radial direction of the circular cross section within the preferred range as described above.

  In the present embodiment, as the dopant, a low molecular compound having a high refractive index, a large molecular volume, not participating in polymerization, and having a predetermined diffusion rate in a molten polymer is used. The refractive index in the radial direction is changed. The dopant is not limited to a monomer, and may be an oligomer (including a dimer and a trimer). Therefore, even if it has polymerization reactivity with the monomer for the core material or the core material 31 in the monomer state, such an oligomer may be used as a dopant if it does not polymerize with these when it becomes an oligomer. it can.

  Specific examples of the dopant include benzyl benzoate (BEN), diphenyl sulfide (DPS), triphenyl phosphate (TPP), benzyl-n-butyl phthalate (BBP), diphenyl phthalate (DPP), diphenyl ( DP), diphenylmethane (DPM), tricresyl phosphate (TCP), diphenyl sulfoxide (DPSO) and the like. Among these, BEN, DPS, TPP, and DPSO are preferable. The refractive index of the POF 23 can be changed to a desired value by adjusting the dopant concentration and distribution in the core material 30.

  A method for manufacturing the preform 21 and the POF 23 will be described. However, the present invention is not limited to the embodiment shown here. First, the first member 14 and the second member 18 constituting the preform 21 are respectively produced. When the first member 14 is manufactured, first, the inner pipe material 12 is manufactured in the inner pipe material manufacturing step 11. At this time, it is preferable to carry out by a vacuum sizing method which is an outer die vacuum suction method using a vacuum sizing die excellent in outer diameter accuracy and the like.

  FIG. 4 shows a pipe material production line 50. The pipe material production line 50 includes a melt extrusion device 51, an extrusion die 52, a forming die 53, a cooling device 54, a take-up device 55, and a vacuum drying device 56. First, the inner pipe material monomer is charged into the melt extrusion apparatus 51. The charged monomer is melted in the melt extrusion apparatus 51, extruded from the extrusion die 52, and sent to the forming die 53. The molding die 53 is provided with a molding tube 57, and the monomer is molded in the molding tube 57 to form a cylindrical hollow molded body. The molding die 53 is provided with a vacuum pump 58. When the monomer is molded, the vacuum pump 58 is preferably used for evacuation. When forming while evacuating in this way, the inner pipe member 12 having a constant thickness can be obtained. When this formed body is sent to the cooling device 54 and cooled, the formed body is cooled and solidified, and the cylindrical inner pipe member 12 is produced.

  The inner pipe member 12 is dried while being reduced in pressure by the reduced pressure drying device 56. The vacuum drying device 56 includes a vacuum pump (not shown) that can reduce the pressure in the interior to a predetermined degree of decompression, and a temperature control that can adjust the internal temperature to a predetermined temperature. Machine (not shown). At the time of drying, in order not to reduce the drying efficiency, it is preferable to maintain the internal pressure reduction degree at 10 kPa or less, and when vapor pressure due to the volatile matter of the material to be dried is generated, it is preferable to adjust appropriately. The temperature at the time of drying is preferably 50 ° C. or more and 100 ° C. or less, and may be adjusted so as to satisfy this range. More preferably, the temperature is near the Tg of the polymer used for the pipe material. .

  Furthermore, the drying time is preferably 10 hours or more and 100 hours or less. In addition, in the production method of the outer pipe member 17 which is the second member 18, the same method as the method of forming the inner pipe member 12 may be used. Also in the second reduced pressure drying step 19, the first reduced pressure drying step 15 and the reduced pressure drying conditions are the same. Moreover, in this embodiment, in the 1st reduced pressure drying process 15 and the 2nd reduced pressure drying process 19, although each process showed the form continuous as the pipe material manufacturing line 50, it is not necessary to make it continue. For example, the pipe material 33 taken up by the take-up device 55 can be temporarily stored and then dried under reduced pressure by the reduced-pressure drying device 56. However, when the storage time becomes long, the moisture content of the pipe member 33 may be improved. Therefore, it is preferable to shorten the storage time as much as possible and proceed to the next step.

  In the present invention, the first member 14 and the second member 18 are produced, and before these are fitted, at least one of the first member 14 and the second member 18 is subjected to the predetermined as described above. Dry under reduced pressure under dry conditions. It is preferable that both the first member 14 and the second member 18 are dried under predetermined drying conditions because moisture, plasticizer, and the like contained therein can be removed.

  Next, as the core material production step 13, the inner clad material monomer is injected into the hollow portion of the produced inner pipe material 12 to form the inner clad material 32. The monomer for the inner clad material is prepared by adding a desired additive (for example, a polymerization initiator, a chain transfer agent, a dopant, etc.) containing methyl methacrylate (hereinafter referred to as MMA) as a main component as a main component. The inner clad material 32 is formed by a rotational polymerization method so as to form a hollow cylindrical shape so that the core material 31 can be formed inside the inner pipe material 12.

  In this rotational polymerization method, the inner clad material monomer is injected into the hollow portion of the inner pipe material 12, and the inner pipe material is preliminarily polymerized while adding vibration in warm water to increase the viscosity of the inner clad material monomer. After that, rotational polymerization is performed while heating in a state in which the longitudinal direction of the inner pipe member 12 is held substantially parallel and substantially horizontal. At this time, the inner pipe member 12 may be rotated in a state in which the longitudinal direction thereof is horizontal. For example, the other end of the inner pipe member 12 is suspended to allow for uniform rotation. The rotation method is not particularly limited, and any method known as a rotation polymerization method can be applied to the present invention.

  The core material monomer is injected into the hollow portion of the inner clad material 32 to form the core material 31. Regarding the monomer for the core material, a polymerization initiator, a chain transfer agent, a dopant and the like are appropriately added to the above-described materials and adjusted, and this is used in International Regret No. 93/08488 pamphlet and Japanese Patent No. 3333292. The GI type core material 31 is formed by applying the described method or the like, and the (GI type) preform 21 is manufactured.

  In the present invention, the method for producing the core material 30 is not limited to the form shown here. For example, it can also be formed by a rotational polymerization method in which interfacial gel polymerization is performed while rotating the core material forming rod. In this case, after injecting the monomer for the core material into the hollow part of the core part forming rod, one end thereof is sealed and the polymerization is carried out by rotating while maintaining the horizontal state in the rotary polymerization apparatus. At this time, the monomer for the core material may be supplied all at once or sequentially or continuously. At this time, by adjusting the supply amount, composition, and degree of polymerization of the monomer for the core material, in addition to the GI type having a distribution in which the refractive index continuously increases toward the center, it has a stepwise refractive index distribution. The present invention can also be applied to the manufacture of multi-step type optical fiber.

  In the fitting step 20, the first member 14 produced by the method as described above is inserted into the hollow portion of the second member 18, thereby fitting the two members together to produce the preform 21 (see FIG. 2). POF 23 can be obtained by drawing the preform 21 by heating and drawing in the drawing step 22. The stretching method in the stretching step 22 is not particularly limited, and any known method can be applied. In addition, before performing the extending | stretching process 22, when the preform 21 is dried under reduced pressure by the process similar to the above-mentioned pipe, it is preferable to aim at reduction of the residual monomer and moisture in the preform 21. As a result, volatile components such as residual monomers and water adhering to and contained therein can be removed, so that these substances can be prevented from volatilizing and foaming during heating and stretching.

  FIG. 5 shows a POF manufacturing facility 60. The POF manufacturing facility 60 is an apparatus used when the preform 21 is drawn while being heated and stretched to produce the POF 23, and includes a drawing furnace 61, an outer diameter monitor 62, and a take-up reel 63. The drawing furnace 61 is a housing that includes a heating furnace 64 and a heater 65 inside thereof, and is provided with an upper opening 66 and a lower opening 67 that serve as a carry-in / out port for the preform 21.

  The preform 21 gripped by a predetermined gripping member is fed into the drawing furnace 61 from the upper opening 66. The gripping member is preferably an adapter connected to a vacuum degree adjusting device. When such an adapter is used, the interface between the first member 14 and the second member 18 can be easily fused by adjusting the degree of vacuum. In this case, the degree of decompression is preferably −10 kPa or more and −0.5 kPa or less with respect to the atmospheric pressure. If the degree of decompression exceeds −10 kPa, the degree of decompression is too high, and the shape of both the first member 14 and the second member 19 may be deformed. On the other hand, when the degree of decompression is less than −0.5 kPa, the degree of vacuum is too low, so that the effect of fusing the first member 14 and the second member 19 to each other is weakened. Further, during stretching, it is preferable to perform the work while rotating the preform 21. Thus, when the preform 21 is rotated during stretching, a columnar POF 23 having a more uniform radius can be obtained. Regarding this rotation method, for example, a rotation device may be connected to the above-described adapter.

  The preform 21 is fed into the heating furnace 64 and stretched while being heated. The heating furnace 64 is provided with a heater 65 for heating the heating furnace 64, and the internal temperature of the heating furnace 64 is adjusted by the heater 65. The heating temperature may be appropriately determined according to the material of the preform 21, but generally it is preferably in the range of 180 ° C. to 250 ° C. Further, stretching conditions such as stretching temperature and stretching tension at the time of stretching may be appropriately determined in consideration of the shape and material of the preform 21 or the POF 23 to be produced. Considering these conditions, the POF 23 is produced by stretching the preform 21 while heating. After the POF 23 is delivered from the lower opening 67, the outer diameter is measured by the outer diameter monitor 62. Based on the measurement result, the desired POF 23 is obtained by stretching while sequentially correcting the drawing conditions. Can do. The heated and stretched POF 23 is taken up by a take-up reel 63.

  As described in Japanese Patent Application Laid-Open No. 7-234322, the drawing tension is set to 0.1 N or more in order to orient the molten polymer, or as described in Japanese Patent Application Laid-Open No. 7-234324. Furthermore, in order not to leave distortion after melt drawing, it is preferable to set it to 1 N or more. Further, as described in JP-A-8-106015, a method of providing preheating at the time of stretching can be used. With respect to the POF 23 obtained by the above method, the breaking elongation and hardness are defined as described in JP-A-7-244220, so that the bending of the optical fiber cable used by bundling the POF 23 or the like Side pressure characteristics can be improved.

  In the present embodiment, after the first member 14 and the second member 18 are produced in separate steps, they are fitted together to form a preform 21, and the preform 21 is heated and stretched to draw, Although the POF 23 was produced while fusing the first member 14 and the second member 18, the present invention is not limited to this form, and when the first member 14 and the second member 18 are fitted together, The POF 23 may be manufactured by drawing the preform 21 by drawing the preform 21 by bonding the mating surfaces using an adhesive.

  A plastic optical cable can be produced by the POF 23 obtained by the present invention. The plastic optical cable has various forms, but is not particularly limited. For example, a collective type in which these are concentrically arranged, or a tape type in which they are arranged in a line can be cited. Moreover, it is preferable that the optical transmission body using the POF 23, the optical fiber cable, or the like according to the present invention is securely fixed to the end portion by using an optical connector for connection. As the connector, various commercially available connectors such as PN type, SMA type, SMI type, F05 type, MU type, FC type, and SC type can be used.

  Since the plastic optical cable obtained from the POF 23 of the present invention has a higher tolerance for the axial deviation than the conventional one, it can be used even if it is joined by butting, but more preferably, it is used for connection at its end. It is preferable to provide an optical connector and securely fix each other's connecting portions. As the connector, various commercially available connectors such as PN type, SMA type, and SMI type that are generally known can be used. Furthermore, various light emitting elements, light receiving elements, optical switches, optical isolators, optical integrated circuits, optical signal processing apparatuses including optical components such as optical transmission / reception modules, and the like are suitably used in combination. In this case, you may combine with another optical fiber strand etc. as needed. Any known technique can be applied as a technique related to them. For example, the basic and actual of plastic optical fiber (published by NTS Corporation), Nikkei Electronics 2001.1.2.3, pp. 110-127 “Printed Wiring You can refer to "This time, optical components are mounted on the board." Combined with various technologies described in the above documents, internal wiring in computers and various digital devices, internal wiring in vehicles and ships, optical terminals and digital devices, optical links between digital devices, general households and housing complexes・ Suitable for optical transmission systems suitable for short distances such as high-speed, large-capacity data communications and control applications that are not affected by electromagnetic waves, including optical LANs in factories, offices, hospitals, schools, etc. Can be used.

  Further, IEICE TRANS. ELECTRON. , VOL. E84-C, No. 3, MARCH 2001, p. 339-344 “High-Uniformity Star Coupler Using Diffused Light Transmission”, Journal of Japan Institute of Electronics Packaging, Vol. 3, No. 6,2000, pages 476 to 480, which are described in “Interconnection by Optical Sheet Bus Technology”, and the arrangement of light emitting elements on the waveguide surface described in Japanese Patent Application Laid-Open No. 2003-152284; , JP-A-2002-90571, JP-A-2001-290055, and the like; JP-A-2001-74971, JP-A-2000-329962, JP-A-2001-74966, JP-A-2001-74968 , JP 2001-318263, JP 2001-31840, etc .; optical branch couplers described in JP 2000-241655, etc .; optical star couplers described in JP 2000-241655, etc .; Optical signals described in Japanese Patent Laid-Open Nos. 2002-101044 and 2001-305395 Optical signal bus system; optical signal processing apparatus described in JP-A No. 2002-23011; optical signal cross-connect system described in JP-A No. 2001-86537; optical described in JP-A No. 2002-26815 Multi-function system described in each publication such as JP 2001-339554 A and JP 2001-339555 A; various optical waveguides, optical splitters, optical couplers, optical multiplexers, optical demultiplexers, etc. In combination, it is possible to construct a more advanced optical transmission system using multiplexed transmission and reception. In addition to the above light transmission applications, it can also be used in the fields of illumination (light guide), energy transmission, illumination, and sensors.

  Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to these examples.

  A melt extrusion apparatus 51 equipped with a φ50 mm diameter screw extruder (Plastics Engineering Laboratory) shown in FIG. A cylindrical hollow molded body having an outer diameter of 25 mm and an inner diameter of 24 mm is extruded using an extrusion temperature of 190 ° C., and then molded using a molding die 53 (manufactured by Plastic Engineering Laboratory) while evacuating with a vacuum pump 57. A molded body was produced. The molded body is fed into the cooling device 54, and the outer surface is cooled and solidified by cooling, and then taken out by the take-up device 55, and then dried under reduced pressure by the reduced-pressure drying device 56 at a temperature of 5 ° C. and 1 kPa or less for 70 seconds. Then, the inner pipe member 12 was produced by cutting to a length of 900 mm.

The inner pipe member 12 having a length of 900 mm was inserted into a polymerization vessel, and this polymerization vessel was washed with ethanol and then dried. After drying, in a state where one end of the inner pipe member 12 is plugged with a stopper 37, the inner clad material monomer is injected into this hollow portion and rotationally polymerized to form a cylindrical hollow inner clad inside the inner pipe member 12. Material 32 was formed. At this time, as the inner clad monomer material, and 205.0g deuterated methyl methacrylate (MMA-d8 manufactured by Wako Pure Chemical Industries, Ltd.), 2,2 ^'- and azobis 0.0881g of (isobutyrate) , 1-dodecanethiol (lauryl mercaptan) 1.318 g, respectively, were mixed and used.

After the inner clad material 32 was polymerized, the core material monomer was injected into the hollow portion and rotationally polymerized in the same manner as the inner clad material 32 to form the core material 31. At this time, the core monomer material, and 141.0g deuterated methyl methacrylate (manufactured by MMA-d8 Wako Pure Chemical Co.), 2,2 ^'- and azobis (isobutyrate) 0.120 g, A light-weight mixed material of 0.526 g of 1-dodecanethiol (lauryl mercaptan) and 10.32 g of diphenyl sulfide (DPS) as a dopant was used. At this time, the surface roughness Ra of the outer peripheral surface of the manufactured first member 14 was set to 0.3 μm.

  Next, a cylindrical hollow outer pipe member 17 as the second member 18 was produced using the same apparatus and conditions as those used for producing the first member 14. At this time, the outer pipe material 17 having an outer diameter of 32 mm and an inner diameter of 25 mm was produced using the same material (PVDF resin) as the inner pipe material monomer as the outer pipe material monomer. At this time, Ra of the inner peripheral surface of the produced second member 18 was set to 0.4 μm.

  After the first member 14 was inserted into the hollow portion of the second member 18 and these were fitted together to produce a preform 21, this preform 21 was produced using a POF manufacturing facility 60 to produce a POF 23. At the time of heating and stretching, stretching is performed at a stretching speed of 3.6 m / min while adjusting the heater 65 so that the internal temperature of the heating furnace 64 becomes 210 ° C. The member 18 was fused to produce a POF 23 having an outer diameter of 500 μm. At this time, after the lower end portion was melted, the pressure was reduced so that the fitted portion was −1.0 kPa with respect to the atmospheric pressure.

  POF23 was produced using the same apparatus, conditions and materials as in Example 1. However, in Example 2, after the first member 14 and the second member 18 were produced, they were fitted into the preform 21 without being dried under reduced pressure.

〔Evaluation methods〕
Using the POF 23 produced in each example, the transmission loss was measured when the load was added to the POF 23 while changing the load over time (Measurement 1). Further, the degree of increase in transmission loss that occurred when the bending radius of each POF 23 was increased was measured (Measurement 2).

  FIG. 6 shows a relationship diagram between the time and transmission loss of each POF 23 in Example 1 and Example 3 obtained in Measurement 1. FIG. From this, it produced using the 1st member 14 and the 2nd member 18 which were dried under reduced pressure with respect to POF23 (Example 2) produced with the 1st member 14 and the 2nd member 18 which were not dried under reduced pressure. In POF23 (Example 1), transmission loss hardly changed even when the degree of load addition was changed. FIG. 7 shows a relationship diagram between the bending radius of each POF 23 obtained in the measurement 2 and the degree of increase in transmission loss. Similar to Example 1, Example 2 had almost no difference in the change tendency of the obtained curve, but compared to Example 1 in which the mating surfaces were dried under reduced pressure to remove the volatile matter between the mating surfaces. Thus, in Example 2, the value of the increase in loss was large overall.

  From the above, the surface roughness Ra between the outer peripheral surface of the first member 14 and the inner peripheral surface of the second member 19 that is the fitting surface between the first member 14 and the second member 19 is adjusted to 0.5 μm or less. It was confirmed that a low transmission loss POF 23 can be produced from the preform 21 produced by fitting the first member 14 and the second member 18 that have been dried under reduced pressure.

It is the schematic which shows the manufacturing process of the plastic optical fiber strand in this invention. It is the schematic of the fitting process which produces preform from the 1st member and the 2nd member. It is a cross-sectional view of POF. It is the schematic of a pipe material manufacturing line. It is the schematic of POF manufacturing equipment. FIG. 5 is a relationship diagram between POF time and transmission loss obtained in an example of the present invention. FIG. 6 is a relationship diagram between the bending radius of POF and the degree of increase in transmission loss obtained in an example of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 12 Inner pipe material 14 1st member 15 1st decompression drying process 17 Outer pipe material 18 2nd member 19 2nd decompression drying process 20 Fitting process 21 Plastic optical fiber preform 23 Plastic optical fiber strand (POF)
50 Pipe material production line 56 Vacuum drying equipment 60 POF production equipment

Claims (6)

A columnar first member comprising a core material made of a core and a clad, and an inner pipe disposed on the outer periphery of the core material;
A second member made of a cylindrical outer pipe disposed on the outer periphery of the first member is produced, and at least one of the first member and the second member is decompressed under a predetermined drying condition. After drying, the first member is inserted into the hollow portion of the second member to form a plastic optical fiber preform, and this is heated and stretched to draw a plastic optical fiber. A method for producing a plastic optical fiber.   2. The method for producing a plastic optical fiber according to claim 1, wherein the temperature during the drying is 50 ° C. or more and 100 ° C. or less, and the drying time is 10 hours or more and 100 hours or less.   The material constituting the core is an acrylic resin, and the core has a refractive index distribution in which a refractive index gradually increases toward a center in a radial direction. Manufacturing method of plastic optical fiber.   The material constituting the second member is characterized in that one kind or two or more kinds of mixed materials obtained by mixing acrylic resin, vinylidene fluoride resin, and polymethyl methacrylate / vinylidene fluoride resin are used. The manufacturing method of the plastic optical fiber strand as described in any one of Claims 1-3.   The thickness of the said 2nd member is 1 mm or more and 100 mm or less, The manufacturing method of the plastic optical fiber strand as described in any one of Claims 1-4 characterized by the above-mentioned. A plastic optical fiber strand manufactured by the method for manufacturing a plastic optical fiber strand according to any one of claims 1 to 5.

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